TOKYO, May 21 (Reuters) - Long-dated Japanese government

bonds saw little relief on Wednesday after a poor auction result

sent yields to record levels and as more debt sales loomed in

the weeks ahead.

Super-long yields have been on the rise, following U.S.

Treasury yields higher and as concerns swirled about new fiscal

stimulus ahead of an upper house election slated for July.

The selloff in bonds is a quandary for the Bank of Japan,

which is trying to taper its debt purchases and normalise

monetary policy. Rising long-term borrowing costs are also a

warning sign for the highly indebted Japanese government.

A lack of buyers at the Ministry of Finance's sale of

20-year JGBs on Tuesday resulted in the worst auction result

since 2012, according to analysts.

"For demand for super-long bonds to rebound, the market

wants to get greater assurance that there will be a reduction of

new bond issuance, which is technically possible within this

fiscal year," said Naoya Hasegawa, chief bond strategist at

Okasan Securities.

"Sentiment will be weighed down ahead of auctions for

30-year bonds next week, and 40-year bonds the week after."

The 20-year JGB yield rose 1.5 basis points

to 2.57% to the highest since October 2000. The yield jumped 15

basis points on Tuesday.

The 30-year yield fell 1.5 basis points to

3.110%, down from a record 3.14%. The 40-year yield

was flat at 3.595% after touching an all-time

peak of 3.6% on Tuesday.

JGBs have been under pressure all year and saw a dramatic

sell-off in March triggered by a slide in German bunds.

Recently, several political parties have been calling for

consumption tax cuts, which Prime Minister Shigeru Ishiba has so

far resisted.

Above-target inflation and the possibility of more fiscal

stimulus are adding to upward pressure on yields, though a

sustained flight from JGBs was unlikely, said Nikko Asset

Management Chief Global Strategist Naomi Fink.

"The move does highlight the need for the Japanese

government to be mindful of its commitment to return Japan to

primary balance," Fink said.

An uptick in inflation portends less bond purchases by the

BOJ, leaving the market vulnerable to the demand of more

price-sensitive buyers, said Sally Auld, chief economist at NAB.

"It sort of feels a bit like the perfect storm for the JGB

market at a time when generally investors seem to be a little

bit more alert or a little bit more worried about the long-end

of yield curves in general and rising term premiums," she said.

The benchmark 10-year JGB yield rose 1.5

basis points to 1.53%. The two-year JGB yield was

flat at 0.725%, as was the five-year yield at

1.005%.

(Reporting by Rocky Swift and Junko Fujita; Editing by Sonia

Cheema and Mrigank Dhaniwala)